Merge pull request rails#8290 from cpatuzzo/master

Fixed a typo

Author: carlosantoniodasilva

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -540,7 +540,7 @@ def type_to_sql(type, limit = nil, precision = nil, scale = nil) #:nodoc:
                 column_type_sql << "(#{precision})"
               end
             elsif scale
-              raise ArgumentError, "Error adding decimal column: precision cannot be empty if scale if specified"
+              raise ArgumentError, "Error adding decimal column: precision cannot be empty if scale is specified"
             end
 
           elsif (type != :primary_key) && (limit ||= native.is_a?(Hash) && native[:limit])